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elpa_solve_tridiagonal(3)   Library Functions Manual   elpa_solve_tridiagonal(3)

NAME
     elpa_solve_tridiagonal - computes the eigenvalue problem for real symmetric
     tridiagonal  matrix  computes all eigenvalues <lambda> and all eigenvectors
     for a real symmetric tridiagonal matrix: T*Q = <lambda>*Q

SYNOPSIS
   FORTRAN INTERFACE
     use elpa
     class(elpa_t), pointer :: elpa_handle

     call elpa_handle%solve_tridiagonal (d, e, q, error)

     With the definitions of the input and output variables:

     class(elpa_t) :: elpa_handle
	    An instance of the ELPA object.

     datatype_real :: d
	    The diagonal elements of matrix T.
	     d is a gloabal array of size elpa_handle%na, replicated on all  MPI
	    ranks.  The  dimensions  of  the  matrix  must  be	set  BEFORE with
	    elpa_setup(3).  On	exit  the  eigenvalues	are  stored  in  d.  The
	    datatype_real    of    the	 diagonal   elements   can   either   be
	    "real(kind=c_double)" or "real(kind=c_float)".

     datatype_real :: e
	    The offdiagonal elements of matrix T.
	     e is a gloabal array of size elpa_handle%na-1,  replicated  on  all
	    MPI  ranks. The datatype_real of the diagonal elements can either be
	    "real(kind=c_double)" or "real(kind=c_float)".

     datatype_real :: q
	    The storage space for the computed eigenvectors Q. The datatype_real
	    of	 the   matrix	can   be   either    "real(kind=c_double)"    or
	    "real(kind=c_float)".

     integer, optional :: error
	    The  return error code of the function. Should be "ELPA_OK". The er-
	    ror code can be queried with the function elpa_strerr(3)

   C/C++ INTERFACE
     #include <elpa/elpa.h>
     elpa_t elpa_handle;

     void   elpa_solve_tridiagonal(elpa_t   elpa_handle,    datatype_real    *d,
     datatype_real *e, datatype_real *q, int *error);

     With the definitions of the input and output variables:

     elpa_t  elpa_handle;
	    The handle to the ELPA object

     datatype_real  *d;
	    The diagonal elements of matrix T.
	     d	is  a gloabal array of size na, replicated on all MPI ranks. The
	    dimensions of the matrix must be set BEFORE with  elpa_setup(3).  On
	    exit  the  eigenvalues are stored in d. The datatype_real can be one
	    of "double" or "float".

     datatype_real  *e;
	    The offdiagonal elements of matrix T.
	     ev is a gloabal array of size na-1, replicated on	all  MPI  ranks.
	    The datatype_real can be one of "double" or "float".

     datatype_real  *q;
	    The storage space for the computed eigenvectors Q. The datatype_real
	    can be one of "double" or "float".

     int  *error;
	    The error code of the function. Should be "ELPA_OK". The error codes
	    can be queried with elpa_strerr(3)

DESCRIPTION
     Computes the eigenvalue problem of a real symmetric tridiagonal matrix. The
     functions	elpa_init(3),  elpa_allocate(3),  elpa_set(3), and elpa_setup(3)
     must be called BEFORE elpa_solve_tridiagonal can be called.

SEE ALSO
     elpa2_print_kernels(1)    elpa_init(3)	elpa_allocate(3)     elpa_set(3)
     elpa_setup(3)  elpa_strerr(3) elpa_eigenvalues(3) elpa_cholesky(3) elpa_in-
     vert_triangular(3) elpa_hermitian_multiply(3)  elpa_uninit(3)  elpa_deallo-
     cate(3)

ELPA				 Thu Nov 28 2024       elpa_solve_tridiagonal(3)

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